1. Field Of The Invention
This invention relates to a wobble plate type refrigerant compressor, and more particularly, to a mechanism for lubricating a radial needle bearing which rotatably supports a drive shaft in the center of a front end plate.
2. Description Of The Prior Art
Referring to FIG. 1, a wobble plate type refrigerant compressor 10 is shown. Compressor 10 includes cylindrical housing 11 comprising cylinder block 111, front end plate 112 and cylinder head 113. A front end plate 112 is mounted on the left end portion of cylinder block 111 by a plurality of bolts (not shown). Cylinder head 113 together with valve plate assembly 13 are mounted on the right end portion of a cylinder block 111 by a plurality of bolts 14. A crank chamber 114 is formed between cylinder block 111 and end plate 112. Opening 112a is centrally formed in front end plate 112 and drive shaft 15 is rotatably supported by a radial needle bearing 16 disposed in opening 112a. Front end plate 112 includes annular sleeve portion 112b projecting from the front surface thereof. Annular sleeve 112b surrounds drive shaft 15 to define a shaft seal chamber 17 in which a shaft seal element 18 is disposed.
Drive shaft 15 is attached to a cam rotor at its inner end by any suitable means so that cam rotor 19 is rotated along with drive shaft 15. Cam rotor 19 is supported on an inner surface of the front end plate 112 by means of a thrust needle bearing 20 disposed at the inner surface of front end plate 112. Wobble plate 21 is disposed on inclined surface of cam rotor 19 through thrust needle bearing 22.
Supporting member 23 comprises shank portion 231 having an axial hole 231a formed therein and a bevel gear portion 232 at the end of shank portion 231. Shank portion 231 is inserted into axial hole 111a which is formed in cylinder block 111. Supporting member 23 is prevented from rotating by means of a key means and key groove (not shown). In addition, supporting member 23 is axially slidable within axial hole 111a. Bevel gear portion 232 includes a seat for steel ball 24 at the center thereof. Bevel gear portion 232 engages bevel gear 25 mounted on wobble plate 21. Steel ball 24 is also positioned in a seat formed at the central portion of bevel gear 25, thereby allowing wobble plate 21 to be nutatably, but not rotatably, supported on steel ball 24. Coil spring 26 is disposed in axial hole 231a of supporting member 231. The outer end of spring 26 is in contract with screw member 27, thereby urging supporting member 23 toward wobble plate 21.
Cylinder block 111 is provided with a plurality of axial cylinders 28 formed therein. Pistons 29 are slidably disposed in cylinders 28, only one piston-cylinder arrangement being shown in FIG. 1. Each piston 29 is connected to wobble plate 21 through a piston rod 30 made of steel. Ball 301 at one end of rod 30 is firmly received in socket 291 of piston 29 by caulking an edge of socket 291, and ball 302 at the other end of rod 30 is firmly received in socket 211 of wobble plate 21 by caulking an edge of socket 211. Balls 301 and 302 slide along an inner spherical surface of sockets 291 and 211, respectively.
Cylinder head 113 is provided with suction chamber 31 and discharge chamber 32. Suction chamber 31 and discharge chamber 32 are separated by partition wall 113a. Valve plate assembly 13 includes valve plate 131 having suction ports 31a connecting suction chamber 31 with cylinders 28 and discharge ports 32a connecting discharge chamber 32 with cylinders 28. Valve plate assembly 13 further includes a suction reed valve (not shown), provided at each of suction ports 31a, and discharge reed valve (not shown), provided at each of discharge ports 32a. Additionally, gaskets (not shown) are provided to seal the mating surfaces of cylinder block 111, valve plate 131 and cylinder head 113. Stopper plate 33 restricts the movement of a discharge reed valve (not shown). Bolt and nut device 34 secures the circular gasket, the suction reed valve, the discharge reed valve, and stopper plate 33 to valve plate 131.
In operation of the compressor, drive shaft 15 is driven by any suitable driving source, such as an automobile engine. Cam rotor 19 rotates with drive shaft 15, causing wobble plate 21 to nutate about steel ball 24 according to the rotation of the inclined surface of cam rotor 19. The nutation of wobble plate 21 causes the reciprocation of each respective piston 29. With each rotation of cam rotor 19, piston 29 cycles through a suction stage in which refrigerant is drawn from suction chamber 31 and a compression stage in which refrigerant is expelled to discharge chamber 32.
While the compressor operates, part of the refrigerant gas in each cylinder 28 passes into crank chamber 114 through a gap between an inner wall of cylinder 28 and piston 29. This refrigerant is known as blow-by gas. In order to return the blow-by gas to suction chamber 31, a passageway (not shown), which is a so-called balance hole, is formed in cylinder block 111 and through valve plate assembly 13 to communicate between crank chamber 114 and suction chamber 31. Lubricating oil is stored in crank chamber 114. During operation, the lubricating oil is agitated, causing some of it to enter a mist state. This mist lubricates the internal moving parts of the compressor. Part of the oil mist in crank chamber 114 flows to suction chamber 31 together with the returning refrigerant gas through the balance hole, and the mist is sucked into respective cylinders 28 to lubricate the gap between pistons 30 and the inner wall of cylinders 28.
Cam rotor 19 is provided with a concave portion 191 on the front surface thereof. Concave portion 191 forms a circular space 35 between front end plate 112 and cam rotor 19. Front end plate 112 has an oil passageway 36 which communicates between space 35 and shaft seal chamber 17. Accordingly, oil flowing along the inner surface of housing 11 flows into space 35 through the gap between thrust needle bearing 20 and front end plate 112, and then flows into shaft seal chamber 17 through oil passageway 36. The lubricating oil in shaft seal chamber 17 flows into the gap between radial needle bearing 16 and drive shaft 15 through the front end of needle bearing 16, and flows into space 35 out the rear end of needle bearing 16.
When lubricating oil lubricates needle bearing 16, the gap between front end plate 112 and cam rotor 19 restricts the amount of oil flowing into space 35. Consequently, the amount of oil flowing into shaft seal chamber 17 is relatively small. Moreover, as the oil flowing into shaft seal chamber 17 accumulates therein, less lubricating oil reaches needle bearing 16. More particularly, after the pressure of the lubricating oil within shaft seal chamber 17 substantially equals that in circular space 35, the lubricating oil flowing through oil passageway 36 significantly decreases. In addition, lubricating oil enters and exits circular space 35 through thrust needle bearing 20. Consequently, there is no circulatory path for the lubricating oil to follow once behind cam rotor 19. With this structure, drive shaft 15 and needle bearing 16 are often insufficiently lubricated, thus allowing drive shaft 15 to flake and potentially ultimately fail.